NITRATE SUPPLY AND POTENTIAL NEW PRODUCTION IN THE BENGUELA UPWELLING SYSTEM

A new method of estimating the potential annual new production of the Benguela upwelling system is presented. With data from the northern and southern Benguela, a negatively correlated regression was established between sea surface temperature (SST) and NO3-N integrated over the depth zone of the biologically productive surface layer. This permitted quantification ot the NO3-N available for production for a specific upwelling event from a NOAA satellite image of SST covering the whole Benguela. The regressed value was considered equivalent to the potential new production of that particular upwelling event and was expressed in carbon terms via the Redfield ratio. This figure was extrapolated to an annual figure by the identification of the number of upwelling events in that year from daily METEOSAT images and supported by synoptic weather maps. The result (4,7 x 10(13) gC . y-1) compared well intra- and inter-regionally and globally. Assumptions implicit in the estimation method and ways of improving the data set upon which the regressions were based are discussed. Any refinements resulting from this would fine tune the result but are thought unlikely to alter the order of magnitude estimation.